This is a note to let you know that I've just added the patch titled
SUNRPC: Optimize xdr_reserve_space()
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sunrpc-optimize-xdr_reserve_space.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 2780155a71abd75d22195eee76024e42e3120e21
Author: Chuck Lever <chuck.lever@xxxxxxxxxx>
Date: Tue Jun 7 16:47:58 2022 -0400
SUNRPC: Optimize xdr_reserve_space()
[ Upstream commit 62ed448cc53b654036f7d7f3c99f299d79ad14c3 ]
Transitioning between encode buffers is quite infrequent. It happens
about 1 time in 400 calls to xdr_reserve_space(), measured on NFSD
with a typical build/test workload.
Force the compiler to remove that code from xdr_reserve_space(),
which is a hot path on both the server and the client. This change
reduces the size of xdr_reserve_space() from 10 cache lines to 2
when compiled with -Os.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Reviewed-by: J. Bruce Fields <bfields@xxxxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h
index 927f1458bcab9..b8fb866e1fd32 100644
--- a/include/linux/sunrpc/xdr.h
+++ b/include/linux/sunrpc/xdr.h
@@ -242,7 +242,7 @@ extern void xdr_init_encode(struct xdr_stream *xdr, struct xdr_buf *buf,
extern __be32 *xdr_reserve_space(struct xdr_stream *xdr, size_t nbytes);
extern int xdr_reserve_space_vec(struct xdr_stream *xdr, struct kvec *vec,
size_t nbytes);
-extern void xdr_commit_encode(struct xdr_stream *xdr);
+extern void __xdr_commit_encode(struct xdr_stream *xdr);
extern void xdr_truncate_encode(struct xdr_stream *xdr, size_t len);
extern int xdr_restrict_buflen(struct xdr_stream *xdr, int newbuflen);
extern void xdr_write_pages(struct xdr_stream *xdr, struct page **pages,
@@ -305,6 +305,20 @@ xdr_reset_scratch_buffer(struct xdr_stream *xdr)
xdr_set_scratch_buffer(xdr, NULL, 0);
}
+/**
+ * xdr_commit_encode - Ensure all data is written to xdr->buf
+ * @xdr: pointer to xdr_stream
+ *
+ * Handle encoding across page boundaries by giving the caller a
+ * temporary location to write to, then later copying the data into
+ * place. __xdr_commit_encode() does that copying.
+ */
+static inline void xdr_commit_encode(struct xdr_stream *xdr)
+{
+ if (unlikely(xdr->scratch.iov_len))
+ __xdr_commit_encode(xdr);
+}
+
/**
* xdr_stream_remaining - Return the number of bytes remaining in the stream
* @xdr: pointer to struct xdr_stream
diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 722586696fade..f66e2de7cd279 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -691,7 +691,7 @@ void xdr_init_encode(struct xdr_stream *xdr, struct xdr_buf *buf, __be32 *p,
EXPORT_SYMBOL_GPL(xdr_init_encode);
/**
- * xdr_commit_encode - Ensure all data is written to buffer
+ * __xdr_commit_encode - Ensure all data is written to buffer
* @xdr: pointer to xdr_stream
*
* We handle encoding across page boundaries by giving the caller a
@@ -703,22 +703,25 @@ EXPORT_SYMBOL_GPL(xdr_init_encode);
* required at the end of encoding, or any other time when the xdr_buf
* data might be read.
*/
-inline void xdr_commit_encode(struct xdr_stream *xdr)
+void __xdr_commit_encode(struct xdr_stream *xdr)
{
int shift = xdr->scratch.iov_len;
void *page;
- if (shift == 0)
- return;
page = page_address(*xdr->page_ptr);
memcpy(xdr->scratch.iov_base, page, shift);
memmove(page, page + shift, (void *)xdr->p - page);
xdr_reset_scratch_buffer(xdr);
}
-EXPORT_SYMBOL_GPL(xdr_commit_encode);
+EXPORT_SYMBOL_GPL(__xdr_commit_encode);
-static __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
- size_t nbytes)
+/*
+ * The buffer space to be reserved crosses the boundary between
+ * xdr->buf->head and xdr->buf->pages, or between two pages
+ * in xdr->buf->pages.
+ */
+static noinline __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
+ size_t nbytes)
{
__be32 *p;
int space_left;
